1. Field of the Invention
This invention relates generally to sight flow indicators for indicating fluid flow through or from a conduit and, more particularly, to a visual sight flexible gas flow indicator having a flexible truncated conical sleeve that connects to a gas conduit or bleeder valve and normally hangs flaccidly in a generally vertical position and becomes fully extended in a generally horizontal position to provide an external visual indication of gas flow or leakage easily seen a distance from the location of the flowing or leaking gas, and reduce the risks of inhalation exposure or asphyxia.
2. Background Art
Typically in industrial plants, such as refineries and petrochemical plants, a vessel, tank or piping system which previously contained hydrocarbons, must be periodically shut down, cleaned, and made safe by “purging” or “inerting” before resuming operations.
“Purging” displaces or flushes out hydrocarbons by introducing substances such as an inert gas, steam or water. Purging a hydrocarbon-filled system with air can create an explosive atmosphere. Using air as a purging gas significantly increases the risk of an explosion. Typically, air forced through a system containing a flammable or combustible liquid residue creates a mist cloud of airborne liquid droplets. Flammable liquid droplets evaporate quickly, and can produce an explosive atmosphere. If there is enough liquid residue, the explosive conditions may persist for a very long time—longer than workers may be willing to wait before beginning their work.
“Inerting” displaces or dilutes the hydrocarbons in the vessel, tank or piping system with an inert (non-flammable and non-reactive) gas such as nitrogen or carbon dioxide, or a compatible inert liquid such as water. The atmosphere must remain non-explosive while workers perform their work. During the work, all ignition sources must be controlled so that they cannot trigger a fire or explosion.
However, the inerting and/or purging operations themselves may create hazards to workers by displacing the oxygen in the environment. If a worker must enter a tank that has been inerted/purged, the proper procedures and protective equipment must be used.
Nitrogen is an inert gas that is colorless, odorless, and tasteless, and because it displaces oxygen, is typically used for purging and inerting, and as a “sweep through” to remove oxygen from vessels, piping and equipment prior to their recommission, and to bring hydrocarbons and other chemicals to a safe “LEL” level (Lower Explosive Limit). The Lower Explosive Limit (LEL) is defined as: The lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat). At a concentration in air below the LEL, there is not enough fuel to continue an explosion. Concentrations lower than the LEL are “too lean” to explode but may still burn violently. as a sweep through to remove oxygen from vessels, piping and equipment prior to its commission
Although workers may be equipped with LEL meters, many LEL meters will not read properly when oxygen levels are less than 10 percent. Without enough oxygen, these meters can give an incorrect low reading even if flammable vapors and gases still remain.
Nitrogen can be very deadly. It can act as an asphyxiant and choke a person to death in less than 40 seconds. Each year many accidents and deaths involving nitrogen occur. Nitrogen displaces oxygen from the air whenever it comes in contact with it. If a continuous flow of nitrogen is released into air, the oxygen level in the air depletes very fast and can choke a person who is breathing this nitrogen-rich air. Thus, a worker who is carrying out a vessel purging and/or inerting operation or a follow-up inspection in a typical petrochemical plant (where the vessel most likely was purged with nitrogen to rid it of explosive vapors), or somebody who is even standing near or in the vicinity of a vessel that has nitrogen purging on, is at risk.
There are a variety of sight indicators known in the art. Typically, these sight indicators are devices that are installed on a pipe and have a window to provide a visual means of verifying liquid flow for direction and approximate rate, and to observe the color and clarity of process fluids passing through the device. One of the problems with these types of sight indicators is that it requires a person to be relatively close to the device in order to observe flow within the pipe on which it is mounted.
Moore, U.S. Pat. No. 3,857,277, discloses a flow indicator comprising a housing having a chamber therein and including inlet and outlet openings communicating with opposite ends of the chamber. A flexible flap hingedly connected to the housing for flexure within the chamber in response to fluid flow through the chamber is visible through a transparent observation port to provide direct indication of fluid flow. A magnet carried by the flap actuates at least one magnetically responsive switch mounted in the housing and adapted for connection in an external circuit to alter the condition of the circuit in response to at least one predetermined flow condition. The flap also functions as a check valve to prevent retrograde fluid flow through the housing.
Brighton, U.S. Pat. No. 5,065,691, discloses a fluid flow indicator for use with light transmitting conduits having end fittings which include a bore. The flow indicator includes a base defined by a coiled wire closely received within the fitting bore and an axially extending indicator support which extends from the base into the conduit includes a rotatable flag whose rotation can be exteriorly observed or sensed as fluid flow occurs. The coiled wire base includes an abutment engaging with fitting structure for axially positioning the indicator relative to the fitting and conduit.
Donehue, U.S. Pat. Nos. 6,526,907 and 7,401,572, disclose a flow indicating device including a tube, a turbine wheel, and a cylinder. The tube defines a flow path. The turbine wheel is mounted in the tube for rotation alongside an inside wall of the tube. The turbine wheel has a plurality of turbine blades. The cylinder is mounted outside the tube for rotation alongside an outside wall of the tube. The cylinder is magnetically coupled to the turbine wheel through the sidewall of the tube so that rotation of the turbine wheel causes rotation of the cylinder. A visually observable pattern is provided on an outside surface of the cylinder so that rotation of the cylinder can be visually ascertained. The device is easy to install and provides an indication of flow within the pipe which is highly visible, easy to read, and viewable from any location around the pipe.
Al-Wehebi, U.S. Pat. No. 7,310,047, discloses a hazardous gases and wind direction sensor that includes a housing having a hazardous gas sensor. The gas sensor sends an output signal to a transmitter at a predetermined frequency upon detecting a hazardous gas. Wind detection is provided by eight LEDs aligned with eight corresponding photocells disposed in the housing, where each photocell represents a topographical direction and is adapted to provide an output signal associated with a particular wind direction at a predetermined frequency. A disk is coupled to a rotatable shaft in the housing and positioned between the LEDs and photocells. The shaft is coupled to a wind direction indicator such as a windsock. The disk has a slot sized to allow light to pass from one of the LEDs to its corresponding photocell, which sends an output signal to enable a switching circuit in the transmitter. The switching circuit enables the output signal at a predetermined frequency to be transmitted to a receiver. The system detects harmful gases in the environment and the direction of the wind, and providing an early-warning system to alert personnel in the vicinity of such dangerous conditions so that they can retreat away from the path of the oncoming harmful gases.
McEwan, U.S. Pat. No. 8,061,389, discloses an apparatus and methods for duct leakage control wherein a sealing element having a “windsock” is introduced into the duct and is automatically drawn or otherwise guided to the locality of a leak; the element being caused, by reason of a pressure differential attributable to the leak, to move into and stem or seal the leak. The sealing element may comprise a plurality of individual members of differing buoyancy, each capable of being carried along at a predetermined level in the duct by the flow of fluid therein. The sealing element may carry a tagging device which can be used to assist in locating the leakage site.